Impact of Large-scale Circulation Patterns on Surface Ozone Variability in Houston-Galveston-Brazoria

Abstract:

The Bermuda High (BH) is a key driver of large-scale circulation patterns for Southeastern Texas and other Gulf coast states in summer, with the expected influence on surface ozone through its modulation of marine air inflow with lower ozone background from the Gulf of Mexico. We develop a statistical relationship through multiple linear regression (MLR) to quantify the impact of the BH variations on surface ozone variability during the ozone season in the Houston-Galveston-Brazoria (HGB) area, a major ozone nonattainment region on the Gulf Coast. We find that the variability in BH location, represented by a longitude index of the BH west edge (BH-Lon) in the MLR, explains 50-60% of the year-to-year variability in monthly mean ozone over HGB for Jun and July during 1998-2013, and the corresponding figure for Aug and Sep is 20%. Additional 30%-40% of the ozone variability for Aug and Sep can be explained by the variability in BH strength, represented by two BH intensity indices (BHI) in the MLR, but its contribution is only 5% for June and not significant for July. Including a maximum Through stepwise regression based on Akaike Information Criterion (AIC), the MLR model captures 58~72% of monthly ozone variability during Jun-Sep with a cross-validation R² of 0.5. This observation-derived statistical relationship will be valuable to constrain model simulations of ozone variability attributable to large-scale circulation patterns.